Ottó Ribári

Cochlear Implantation Influences Contralateral Hearing and Vestibular Responsiveness

A cochlear implant program has been carried out at the ORL Clinic of Semmelweis University in Budapest since 1985. Different devices and techniques have been used in pre- and postlingual children and adults. Over the last 6 years contralateral hearing improvement has been observed in 18 patients. This phenomenon can usually be demonstrated 6 months after the operation. Since our first observation several other authors have confirmed this phenomenon. However, the underlying mechanism is still obscure; both the efferent innervation and the plasticity of the brain may be important factors. The vestibular function of cochlear implant candidates was checked routinely pre- and postoperatively and changes in vestibular responsiveness were observed. Over the last 3 years air-caloric stimulation has been performed by means of a computer-based ENG system. In most patients the vestibular function was unchanged after the implantation. but in some cases a significant improvement in vestibular responsiveness was noted. Here we briefly describe cases of re-implantation carried out at the clinic. All the patients obtained better speech discrimination scores after having been implanted with intracochlear devices. None of the patients suffered any inner ear abnormality due to the first implant.

Intracellular calcium and outer hair cell electromotility

The influence of increased intracellular calcium level on outer hair cell (OHC) electromotility was examined by means of transcellular electrical stimulation in a partitioning microchamber. Electromotile activity was measured before and after application of the calcium ionophore ionomycin, which promotes the inflow of extracellular calcium, as well as its release from intracellular calcium stores. The ionomycin solvent, dimethyl sulphoxide (DMSO), by itself elicited a significant decrease in the magnitude of OHC electromotility. The DMSO effect was counteracted by 10 microM ionomycin and was reversed by 50 microM ionomycin. The increase in electromotility is partially mediated by a calmodulin-dependent mechanism, since W7, a calmodulin antagonist, attenuated the 50 microM ionomycin-induced motility increase. Our results suggest that the electromotility magnitude increase in isolated OHCs due to ionomycin is a calcium/calmodulin-dependent phenomenon.

Intracochlear injection of pseudorabies virus labels descending auditory and monoaminerg projections to olivocochlear cells in guinea pig

Pseudorabies virus was used to label transneuronally descending auditory projections following intracochlear injections. At different time points after injection, virus‐infected cells were detected immunohistochemically in the central nervous system. Initially (25 h), virus was transported retrogradely to olivocochlear cells in the pons. At 32–72 h after injection, labelling occurred in higher order auditory brainstem nuclei as well as in the locus coeruleus and pontine dorsal raphe. At 90–108 h, virus‐infected neurons were found bilaterally in the medial geniculate body and in layer V of the auditory cortex. Viral transneuronal labelling in the auditory cortex after intracochlear application confirms the existence of a continuous descending chain of neurons from the auditory cortex to the cochlea, via the medial and lateral olivocochlear systems. The transneuronal labelling of the locus coeruleus and pontine dorsal raphe suggests that noradrenergic and serotonergic inputs may substantially influence the activity of olivocochlear cells, and thus the cochlea.

Air caloric computer system application in monitoring vestibular function changes after cochlear implantation.

INTRODUCTION: The computer-based ENG systems analytical routine refinements are available only in research laboratories. The computer-based system contains a stimulator for saccadic eye-movement and an air caloric stimulator interconnected to the registration program and analysis software. Several authors have reported the preoperative and postoperative vestibular functions in cochlear implant patients. The safe examination of the operated ear and comparison of the preoperative and postoperative average slow phase velocities of the caloric nystagmus is possible using the air caloric computer system. METHODS: The authors have used a computer-based ENG system with caloric air stimulation, which is very useful for examination of the operated ear. The vestibular system of patients with total deafness was examined before and after the cochlear implantation. The results of 60 vestibular examinations of 64 patients are reported. RESULTS: The vestibular function in the operated ear was found unchanged in 20 patients. In 14 patients the vestibular function was worse. In 16 patients the postoperative vestibular responsiveness improved. The detailed data analysis of 10 patients in whom preoperative and postoperative vestibular examination was similar was performed by the authors. The preoperative and postoperative average slow phase velocity values and the relative canal paresis was observed. The values demonstrated that the caloric responsiveness of the operated ear improved in few cases. CONCLUSIONS: The computer-based air caloric system is a useful and safe method in evaluation of the vestibular system changes after ear surgery. The reason of the improvement of vestibular responsiveness is not clear. The results need further investigation to solve the problem of vestibular responsiveness improvement after cochlear implantation.

Cathepsin-B activity in otosclerosis

SummaryCathepsin-B activity was determined fluorimetrically in the otosclerotic stapes footplate, the stapes superstructure, normal temporal cortical bone, and os frontale osteoma. Measurements with a synthetic substrate made determinations in individual samples possible. The cathepsin-B activity in the otosclerotic stapes footplate was one order of magnitude higher than that of the superstructure, which was not affected by the disease. The cortical bone and the superstructure displayed similar activities, as did os frontale osteoma and otosclerosis. The high lysosomal proteinase activity appears to be closely connected to the otosclerotic bone resorption process.

Inhibition of myosin light-chain kinase activity in the organ of Corti by 0.3–5 kilodalton substances of the otosclerotic perilymph

SummaryThe guinea pig organ of Corti contains myosin light-chain kinase (MLCK) activity. The upper and lowermost parts of the cochlea do not show significantly different activities of the enzyme, which is Ca2+ and calmodulin-dependent. Short-term noise exposure does not cause a significant change. 0.3–5 Kilodalton substances of the otosclerotic perilymph, separated by SG-25 column chromatography, inhibit the MLCK activity in in vitro organ of Corti preparations. This inhibitory action of the perilymph substances can also be observed with the purified MLCK of turkey gizzard. The activity of the enzyme can be specifically inhibited by cyclic AMP-dependent protein kinase.

Search for Prognostic Factors in Head and Neck Cancer

Fifteen patients with head and neck carcinoma were treated with irradiation (14-70 Gy telecobalt). Apoptotic and mitotic index, DNA index, ratio of cells in S phase, p53 protein overexpression in untreated tumours as well as the changes of these parameters after the first 2 Gy irradiation except proliferative kinetics parameters were examined in order to determine the prognostic value of these factors. The data show that inducibility of apoptosis is very low in head and neck carcinomas which correlate with the unfavourable prognosis. The decrease in mitotic index after the first 2 Gy irradiation, which occurred in 7 cases--5 of them still alive--indicates a better chance for relatively longer survival. In immunohistochemically p53 positive tumours frequently occurring aneuploidy and elevated S-phase rate were found.

Oversulfated Mucopolysaccharides in the Otosclerotic Bone

Mucopolysaccharides (glucosaminoglycans, GAGs) were extracted from otosclerotic and non-otosclerotic human stapes footplate, stapes superstructure and guinea pig stapes footplate. Cellulose acetate electrophoresis revealed an unknown highly anionic band (Rf = 1.05) beside the conventional hyaluronic acid, chondroitin sulfate and heparan sulfate fractions. Chemical analysis resulted in a high sulfate/hexosamine molar ratio in the otosclerotic GAG extract (1.7 and 1.9) and a very low ratio in non-otosclerotic human stapes and normal guinea pig stapes footplate GAG extract (0.20 and 0.21, respectively). Hexuronic acid content was highest in guinea pig stapes GAG preparation. Our results serve as indirect evidence of the presence of an oversulfated GAG fraction in the otosclerotic bone, which can potentially initiate otosclerotic bone resorption.

Cathepsin D Activity in Otosclerotic Bone and Perilymph

Otosclerotic bone and perilymph samples obtained during stapedectomy operations from patients suffering from pure conductive hearing loss of at least 40 dBs air-bone gap at 500 Hz. Control perilymph samples derived from patients suffering from round window membrane rupture or Menieres disease. Enzyme activities were determined using a synthetic fluorogenic substrate by fluorescence spectrophotometry. No significant differences have been found between the protein content of otosclerotic and normal or non-otosclerotic perilymph samples. Cathepsin D activity was significantly higher (p less than 0.001) in the otosclerotic perilymph samples. Otosclerotic stapes footplate contained more activity than normal meatal cortical bone as well, though the difference was not significant. Biological significance of the elevated Cathepsin D activity must be considered.

The barrier-like role of activated connective tissue against the spread of supraglottic laryngeal carcinoma

SummaryLight microscopic investigations of whole organ serial sections of 15 laryngectomy specimens with supraglottic carcinomas and comparative electron microscopic studies of the upper and lower poles of the tumors were carried out. The ultrastructure of different poles of the same supraglottic tumors was investigated and showed a more progressive fibrillogenesis with an activation of the connective tissue elements of the border on the lower pole of the malignancy. A significant role is attributed to the barrierforming feature of activated connective tissue with respect to the inhibition of the extension of tumor into the glottic region.